Mr Joyce said he did not want to create two classes of people - those who can afford power, and those who can't - by refusing the mine.

"I'm going to be a complete economic pragmatist. We have to make sure this economy works. We have to export dollars. One of our largest exports is coal," he said.

"We have to realise we have a moral responsibility to other people in other nations to keep their lights on. They have their right to exist in the 21st century like we do. We can't sort of lord it over people and say 'we prescribe a way of life for you that you can't afford'."

Mr Joyce said the mine would ultimately lead to lower emissions than if people in India used local coal.

"If we decide that we don't want to use Adani - the coal from the Galilee coalfields - to help poor people in India be able to turn on their lights like we do, they're still going to get coal. They're just going to get coal that's 60 percent less efficient, from India," he said.

"So you're actually going to increase your carbon emissions."

Mr Joyce was also quizzed on climate change. He acknowledged human activity had an impact on the phenomenon, but said it was not responsible for "every climatic catastrophe".

"Of course, if human activity is putting greenhouse gases - and it does - into the atmosphere, then of course that has an effect on the climate," he said.

"They [activists] always take the next step and say 'that cyclone was climate change, that bushfire was climate change', everything. And it's not. It's part of the natural path of what happens in the climate all the time, for which part of the effect are greenhouse gases."

Fellow panellist Brian Schmidt, the vice chancellor of Australian National University, said we must take steps over the next 30 years to lessen the impact of climate change.

"You are correct that often any little thing is ascribed to climate change," said Mr Schmidt, who won the Nobel Prize for physics in 2011. "But as climate change becomes bigger and bigger, more and more things really are going to relate to that.

"People have, I think, this false belief that it's only going to be two degrees [of warming]. It's only going to be two degrees if we actually really start changing quickly. It could be five, six, seven - we don't know, it's hard to calculate when it becomes really big."